Method and apparatus for maximizing the viewing zone of a lenticular stereogram

ABSTRACT

A lenticular stereogram has an improved viewing zone for a specific viewing distance when an image print ( 207 ) having an optimum image column width is utilized. The optimum image column width is determined by observing a series of two color prints having variable image column widths mounted under a lenticular screen ( 206 ) through an imaging apparatus.

FIELD OF THE INVENTION

This invention relates to three dimensional stereoscopic print images,also known as lenticular stereograms or parallax panoramagrams, and moreparticularly, to a method and apparatus for increasing the viewing zoneof images in lenticular stereograms.

BACKGROUND OF THE INVENTION

Lenticular stereograms have been used for many years to display a truethree-dimensional stereoscopic image without the need for the observerto wear special selection devices which selectively permit the left eyeand right eye to see different images. Selection devices are typicallyeyeglasses that are colored (red/green) or polarized so that a leftimage and a right image can be viewed from one source. The lenticularstereogram is made by photomechanical reproduction and most commonlyused for trading cards, picture postcards, product displays, and thelike. By incorporating a cylindrical lenticular screen which has acorduroy-like surface over a properly encoded image print, astereoscopic three dimensional depth effect may be achieved.

As shown in FIG. 1A, the lenticules 101 have semi-cylindrical surfacesoriented so that their lengths are aligned vertically. The lenticulesare in intimate juxtaposition with a print image 102, which containscolumns of encoded visual information. Each column of the print image102 is associated with a particular lenticule, and each column has aseries of views ranging from a leftmost to a rightmost perspective.Thus, instead of seeing a single image as in a normal print, theobserver of a panoramagram will see perspective images for both the leftand right eyes due to the refractive nature of the lenticular surface ofthe panoramagram. More specifically, because the left eye views thelenticular stereogram from different angles than the right eye, each eyehas a different view of the image creating a three dimensional image.

Although the art of making lenticular stereograms is continuing toadvance, a number of persistent problems remain which inhibit the mediumfrom becoming more pervasive. In particular, lenticular stereograms havea limited range of points at which they can be viewed withoutdegradation of the three-dimensional image due to the parallax effect.To properly view the entire print or display, all columnar structuredimages and associated columnar lenticules must be in intimatejuxtaposition. The center of an image is typically viewed at a nearperpendicular angle, while the left and right edges of the image may beviewed at much more acute angles. The parallax effect occurs at acuteviewing angles and creates a lack of precise juxtaposition between thecolumnar structured image and the associated columnar lenticules. Thelack of juxtaposition occurs because at a highly acute angle, the focalpoint of the lenticule is not properly on the associated print columnand an inaccurate columnar image is viewed.

The range of points at which the full and accurate three-dimensionallenticular stereogram image can be seen is known as the “viewing zone.”There have been prior art attempts to maximize the viewing zone byreducing the parallax effect. For example, U.S. Pat. No. 5,838,494discloses a mathematical technique for adjusting the width of the printcolumns to match the width of the lenticular screen to optimize theviewing zone, but requires obtaining screens with precise lenticulewidth dimensions. U.S. Pat. No. 5,083,199 requires an air gap to improvethe lenticular stereogram viewing zone and it is not clear if paperprints will work with this method. Also, the lenticular screen isimposed on a curved structure with varying lenticule widths which isvery difficult to manufacture. The article by E. Sandor et al. entitled“Technical Info on PHSColorgrams®” (see generallyhttp://www.artn.nwu.edu) discloses increasing the viewing zone of alenticular stereogram by using print columns which are wider than thewidth of their corresponding lenticules but does not disclose a methodfor coordinating the width of the print with the width of thelenticules. Thus, none of these references provides a simple solutionfor maximizing the viewing zone of a lenticular stereogram.

The present invention sets out to provide a simple method for increasingthe viewing zone of a lenticular stereogram.

SUMMARY OF THE INVENTION

The present invention is a simple method for increasing the viewing zoneof a stereographic image which may be a photographic print, a projectedor computer-generated image, or any other type of graphical image. Theviewing zone is improved by determining the optimum column width for theimage columns of the stereographic image. The optimum column widthprovides optical alignment for each column with its correspondinglenticule for a specified viewing position. The optimum column width maybe determined empirically with a series of test images. Once determined,stereographic images having the optimum column width can be producedusing an interdigitation program.

Each test image has a plurality of columns each corresponding to asingle lenticule of the lenticular screen. Each column has two singlecolor stripes where the colors are discernible or visually distinct fromeach other. The colored stripes thus alternate over the complete widthof the test image.

The optimum column width is determined by viewing the test image andlenticular screen with a viewing apparatus having a left eye viewingposition and a right eye viewing position. When the image appears to beone color when observed from the left eye viewing position and the othercolor when observed from the right eye viewing position, then theoptimum column width has been achieved. The test image having theoptimum column width can be determined by viewing a series of such testimages having different column widths. Stereographic images can then beproduced using the optimum column width and the viewing zone will bemaximized when a center column of the stereographic image is alignedwith a center lenticule of the lenticular screen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective drawing showing the structure of a lenticularstereogram.

FIG. 1B is a perspective drawing showing the structure of an individuallenticule and corresponding interdigitated image from the structure ofFIG. 1.

FIG. 1C is a perspective drawing showing the test target for calibratingthe pitch of the print with respect to the pitch of the lenticularscreen.

FIG. 2 is a drawing of the apparatus used to locate the observer whileadjusting the lenticular screen and test target.

FIG. 3A is a schematic representation of a lenticular screen and printcolumns viewed from an observation point without making the necessaryadjustment to optimize the viewing angle.

FIG. 3B is a schematic representation of a lenticular screen and printcolumns viewed from a remote observation point.

FIG. 3C is a schematic representation of a lenticular screen and printcolumns showing the necessary adjustment to optimize the viewing angle.

FIG. 4 is a test border and columnar stereogram print or projecteddisplay.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1A, a portion of a lenticular screen 101 andassociated print 102 is illustrated. The term “print” is used broadly tosignify any well-known displays, such as a rear-projected display, aphotographic print, a photomechanically-reproduced print, or anelectronic display screen, as well as combinations of these knowndisplays. The print 102 is fixed in intimate juxtaposition with thelenticular screen 101 such that two parallel planes are referenced: theplane of print 102 is defined by points ADLI and the reference plane ofthe lenticules is defined by points EHPM. The lenticules are individualcylindrical lenses, EFNM, FGON and GHPO having cylindrical surfacesillustrated as equal radius arcs EF, FG and GH, and corresponding arcsMN, NO and OP respectively. The lenticule screen is overlaid on top ofreference plane EHPM and each lenticule is optically aligned in intimatejuxtaposition with a corresponding rectangular print area on print 102to provide different images or views from different viewing angles. Forexample, print area ABJI is directly behind and intimate juxtapositionwith lenticule EFNM.

Referring to FIG. 1B, a more detailed illustration of the print areaABJI and corresponding lenticule EFNM is shown. The print area 102 issubtended by five columns or stripes 1, 2, 3, 4 and 5. Any number ofcolumns may be used, but for simplicity only five columns areillustrated. Because of the optical properties of the lenticule, onlyone stripe can be seen from any one viewing position. Stripe 1 containsthe rightmost view and as the point of view moves from right to leftstripes 2, 3, 4 and 5 are viewed sequentially.

The production of this kind of interdigitated stereogram print is wellunderstood. In the exemplary five column stereogram, five perspectiveviews are produced by five cameras pointing straight ahead equidistantfrom each other and taking photographic images simultaneously. Theseimages may be either captured digitally or by conventional photographicmeans and then digitally scanned. These digital images are then slicedup using an interdigitation software algorithm and reassembled as astereogram print. The stereogram print is fabricated by havingindividual perspective image views interdigitated (sometimes mistakenlyreferred to as “interleaved”) so that the print area which correspondsto a particular lenticule is made up of a number of discrete stripes.When viewing a lenticular stereogram made up of five interdigitatedimages, five distinct image views may be seen by looking at thelenticular stereogram from five different ranges of angles.Interdigitation algorithms and software are well known in the art. Anexemplary interdigitation algorithm is described in detail inInternational Publication No. WO 98/27456 which is hereby expresslyincorporated by reference.

FIG. 3A illustrates the parallax problem. A lenticular print is shown tobe within the extent of bracket 301A. For simplicity, only threerepresentative lenticules 303, 305, and 307 and their correspondingprint areas 309A, 310A and 311 A are illustrated. As discussed, anynumber of lenticules and columns may be used. An observation point 302is centrally located with an on-axial view of the lenticular print,directly above the central lenticule 305. (A perpendicular dropped fromobservation point 302 would intersect the horizontal center of the printand lenticule 305.) Rays of light which are observed from observationpoint 302 are refracted by lenticules 303, 305 and 307 and have focalpoints at 304, 306 and 308, respectively. The parallax problem in thisexample results from the focal points 304 and 308 being out of alignmentwith their corresponding print areas. In FIG. 3A, the focal points 304and 308 are completely off of the print areas 309A and 311A respectivelyand therefore not viewed at all from observation point 302. Thus, onlythe print image near the central area 310A appears to be stereoscopic.Images on either side of the center of the print may appear to bedistorted or confusing because the eyes will be seeing portions ofcolumns and their correspond stripes that do not correspond to a properstereoscopic image. Under such circumstances the eyes might well beseeing a left image with the right eye and a right image with the lefteye. Thus, without precise corrective shifting of the print columnsrelative to the lenticules, the range of viewing angles within theviewing zone is substantially reduced.

The parallax problem diminishes as the distance between the observationpoint 302 and the print increases. Referring to FIG. 3B, if theobservation point (not shown) is a substantial distance from the print,the light rays from the lenticules to the observation point are moreparallel and the focal points 304, 306 and 308 fall within the printareas 309B, 310B and 311B, respectively. From this observation point,the print areas 309B and 311B do not require shifting because theparallax problem does not exist and edges of prints. Thus, to avoid theparallax problem, lenticular screens of greater width must be viewedfrom greater distances than narrower prints to reduce the acute viewingangle at the left and right sides of the print.

In order to view an entire stereoscopic image, the focal points of allof the lenticules must fall within the boundaries of the print areas,corresponding to each of the lenticules. FIG. 3C illustrates anembodiment of a lenticular stereogram in which the focal points of allthe lenticules fall within their corresponding print areas which havebeen horizontally shifted. The shifted print areas eliminate theparallax problem and allows the full image to be viewed from anobservation point where the light rays between the observation point andlenticules are not parallel. The parallax problem is compensated for byhorizontally shifting the print areas 309C and 311C relative to thelenticules 303 and 307 so that the focal points 304 and 308 are incidentupon the centers of print areas 309C and 311C respectively. Print area310C does not require shifting because the focal point 306 is alreadyincident close to the center of the print area 310C.

In general, full stereoscopic image projection requires that the printcolumns on the left side of the print be shifted to the left and thatthe print columns on the right side of the print be shifted to the rightfor the focal point of each lenticule to fall upon the proper print areacolumn. The distance which each column is horizontally shifted is afunction of the angle at which each print column is observed isinversely proportional to the distance between the viewing point and thelenticular screen. The shifting of print area columns increases as theobservation point gets closer to the lenticular screen.

The inventive technique for maximizing the viewing zone of a lenticularstereogram uses the lenticular screen as a calibration and measurementtool to determine the optimum print column width for a specific viewingdistance. FIG. 1C shows an embodiment of the present invention having alenticule 106 and a corresponding print area 105 which is made up of twostripes 103 and 104. In the inventive technique, these two stripes areof complementary or contrasting color. For example, stripe 103 andstripe 104 may be black and white, or magenta and cyan, or green andred, respectively or any other condition of distinguishable colors. Fullsized stereographic image prints with contrasting colors having precisecolumn widths may be produced with an interdigitation computer program.Thus, a series of two color test prints can be made having anincrementally different image column widths. Image prints can beproduced having a column width accuracy of 0.01 inch or better.

The two color test prints may be used with a stereogram image viewingdevice to determine the optimum image print column width for a specificviewing position. A lenticular stereogram image print produced with anoptimum print column width will be fully viewable and have optimal threedimensional appearance. Because a single image print column width cannotbe optimally viewed from all positions, the image print column width isdesigned for a specific viewing distance. Generally, the lenticularstereogram is designed to be viewed from a central position, however thedistance at which the lenticular stereogram is viewed is variable.

A stereogram image viewing devices may be used to view the two colortest prints from a specific viewing position. An embodiment of astereogram image viewing device is illustrated in FIG. 2 and includes: alocation device 201 having eyeholes 202 and 203, a post 204 and abaseboard 205. The post 204 rigidly holds the location device 201 overthe baseboard 205. The lenticular screen 206 is placed in intimatejuxtaposition with the print 207 such that the center lenticule isdirectly over the center print column. The aligned print 207 andlenticular screen 206 are placed directly under the viewing device 201,such that the lenticules are vertically oriented relative to the viewerand the center of the print 207 is centered below a mid-point 208between eyeholes 202 and 203. A viewer observes the print 207 throughthe eyeholes 202 and 203. In an alternative embodiment, digital camerasare positioned to view the print 207 as if from eyeholes 202 and 203.

If the width of the print columns is optimum with the focal points ofthe lenticules each falling upon proper columns of the print areas (asillustrated in FIG. 3C), the image 207 will appear to be one uniformcolor from eyehole 202 and the complementary or contrasting uniformcolor from eyehole 203. Imperfections in the test print or lenticularscreen may cause slight imperfections in the viewed images. A test printhaving an improper print column width will not appear to be uniform incolor. By observing a series of test prints with different print imagecolumn widths through the stereogram viewing device, the print havingthe most uniform observed colors from the eyeholes 202 and 203 may berapidly determined. The best column width dimension for this test printis input into the interdigitation program to produce stereographic imageprints having the optimum image column width and an optimized viewingzone.

Observation of the print through the stereogram image viewing apparatusand lenticular screen is a highly accurate measurement tool which allowsthe optimum print image column width to be quickly determined. In theart, the term pitch is often used to describe the print column width orthe lenticule width. Pitch is the number of columns, or number oflenticules, per inch. If the print/lenticular screen combination isviewed from some great distance, the pitch of the print columns andlenticules are equal. In another example, at a viewing distance of 3feet, a lenticular screen having a nominal pitch of 58.23 produces amaximum viewing zone when used with a print having a pitch of 58.35,i.e. 58.35 columns per inch. A stereographic print which has beenoptimized for a viewing distance of three feet also produce goodstereographic imaging from a viewing distance of approximately two tofive feet.

There are also many variations in the basic inventive technique. Theinventive technique may be used for rear-projection slides as well ascalibration or alignment of motion pictures, electronic images andlenticular screens used with electronic displays and combinations ofthese known displays. In particular computers may incorporate alenticular screen and an interdigitation program which allows the testimages to be projected so that the optimum viewing zone may bedetermined for a particular user. The computer would then displaystereographic images having the optimum column width magnification inoptical alignment with the lenticular screen. Alignment of the projectedimage with the lenticular screen may be achieved via the displaycontrols or software.

In another embodiment, a series of print patterns having differentcolumn widths that may be viewed from a single location by a single eye.An appropriate series of test patterns having different columndimensions may be used to empirically calibrate the optimum width andlocation of the image print columns with respect to the lenticules andoptimize the viewing zone.

In another embodiment, a two color test print may also be combined withimage prints for alignment purposes. Referring to FIG. 4, a print 401having a two color border pattern 407 and a picture area 402 may bealigned using the described alignment method with a lenticular screensuch that the viewing zone is located centrally over the of the print401 and not skewed to the left or right. A lenticular screen is placedover the print 401 and the print 401 is viewed through the stereogramviewing device. The two color border pattern 407 is then aligned andcentered with the lenticular screen when the border appears to be onecolor when viewed with the right eye and the contrasting color whenviewed with the left eye.

Again referring to FIG. 4, in another embodiment, a first two colorpattern may be used in horizontal border areas 405 and 407 and a secondtwo color pattern of another type may be used for the vertical borderareas 403 and 404. For example, alternating black and white stripes maybe used within the columns of vertical regions 403 and 404, andalternating red and green stripes may be used for the horizontal regions405 and 406. The black and white stripes in regions 403 and 404 may beused for rotational alignment of the lenticules with respect to thestereographic print columns. Observing the print through the imagingdevice, the one eye will observe the vertical border areas 403 and 404as black and the other eye will observe the vertical border areas 403and 404 as white. The red and green stripes in regions 405 and 406 maybe used for central alignment of the stereographic print with thelenticular screen by aligning the two color column at the center of theprint 401. Again one eye will see regions 405 and 406 as green and theother eye will see regions 405 and 406 as red.

A method for maximizing a viewing zone of a lenticular stereogram hasbeen described. Although the present invention has been described withreference to specific exemplary embodiments, it will be evident thatvarious modifications and changes may be made to these embodimentswithout departing from the broader spirit and scope of the invention asset forth in the claims. Accordingly, the specification and drawings areto be regarded in an illustrative rather than a restrictive sense.

I claim:
 1. A method of optimizing the viewing zone of a lenticularstereogram, comprising: a. providing a test image in intimatejuxtaposition with a lenticular screen, wherein the test image includesa plurality of columns each corresponding to an individual lenticule ofthe lenticular screen, and wherein each column of the test image has apredefined column width and includes at least a first stripe of a firstcolor and a second stripe of a second color alternating with each other,and wherein the first color and the second color are visually distinct;b. observing the test image and lenticular screen from a specifiedviewing position with a viewing device, wherein the viewing deviceincludes a first eye perspective viewer and a second eye perspectiveviewer; c. determining an optimum column width for an interdigitatedstereoscopic image, wherein the optimum column width is obtained whenthe first color is observed with the first eye perspective viewer whilethe second color is observed with the second eye perspective viewer instep b; d. providing a modified test image if the optimum column widthis not obtained in step c and then repeating steps b and c with themodified test image, wherein the modified test image is identical to thetest image except that the column width is altered; and e. producing astereoscopic image for use in a lenticular stereogram, wherein thestereoscopic image includes interdigitated columns each having theoptimum column width.
 2. The method of optimizing the viewing zone of alenticular stereogram of claim 1, further comprising aligning a centralone of the plurality of columns with a center lenticule of thelenticular screen.
 3. The method of optimizing the viewing zone of alenticular stereogram of claim 1, wherein the first color contrasts withthe second color.
 4. The method of optimizing the viewing zone of alenticular stereogram of claim 1, wherein the first color and the secondcolor are selected from the group consisting of: black and white,magenta and cyan, or green and red, respectively.
 5. The method ofoptimizing the viewing zone of a lenticular stereogram of claim 1,wherein an interdigitation program is used to adjust the column width ofthe plurality of columns.
 6. The method of optimizing the viewing zoneof a lenticular stereogram of claim 1, wherein a pair of human eyes areused to view the test image from the first eye perspective viewer andfrom the second eye perspective viewer.
 7. The method of optimizing theviewing zone of a lenticular stereogram of claim 1, wherein a pair ofdigital cameras are used to view the test image from the first eyeperspective viewer and from the second eye perspective viewer.
 8. Amethod of optimizing the viewing zone of a lenticular stereogram,comprising: a. providing a plurality of test images, wherein each testimage has a plurality of columns each having the same column width andwherein the column width differs by a known amount for each test image,and wherein each column includes at least a first stripe of a firstcolor and a second stripe of a second color alternating with each other,and wherein the first color and the second color are visually distinct;b. holding a first of the test images in intimate juxtaposition with alenticular screen; c. observing the test image from a specified viewingposition with a viewing device, wherein the viewing device includes afirst eye perspective viewer and a second eye perspective viewer, d.determining an optimum column width for an interdigitated stereoscopicimage, wherein the optimum column width is obtained when the first coloris observed with the first eye perspective viewer while the second coloris observed with the second eye perspective viewer in step b; e.substituting another of the test images if the optimum column widthmagnification was not obtained in step d and repeating steps b, c and d;and f. producing a stereoscopic image for use in a lenticularstereogram, wherein the stereoscopic image includes interdigitatedcolumns each having the optimum column width.
 9. The method ofoptimizing the viewing zone of a lenticular stereogram of claim 8,further comprising aligning a central interdigitated column of thestereoscopic image print or the projected image with a center lenticuleof the lenticular screen.
 10. The method of optimizing the viewing zoneof a lenticular stereogram of claim 8, wherein the first color contrastswith the second color.
 11. The method of optimizing the viewing zone ofa lenticular stereogram of claim 8, wherein the first color and thesecond color are selected from the group consisting of: black and white,magenta and cyan, or green and red, respectively.
 12. The method ofoptimizing the viewing zone of a lenticular stereogram of claim 8,wherein an interdigitation program is used to produce the plurality oftest prints or the plurality of test projected images.
 13. The method ofoptimizing the viewing zone of a lenticular stereogram of claim 8,wherein a pair of human eyes are used to view the test print from thefirst eye perspective viewer and from the second eye perspective viewer.14. The method of optimizing the viewing zone of a lenticular stereogramof claim 8, wherein a pair of cameras are used to view the test printfrom the first eye perspective viewer and from the second eyeperspective viewer.
 15. A method of optimizing the viewing zone of alenticular stereogram, comprising: a. providing a plurality of testimages, wherein each test image has a plurality of columns each havingthe same column width and wherein the column width differs by a knownamount for each test image, and wherein each column includes at least afirst stripe of a first color and a second stripe of a second coloralternating with each other, and wherein the first color and the secondcolor are visually distinct; b. holding a first of the test images inintimate juxtaposition with a lenticular screen; c. observing the firsttest image from a specified viewing position with a viewing device,wherein the viewing device includes a first eye perspective viewer and asecond eye perspective viewer, d. determining an optimum column widthfor an interdigitated stereoscopic image, wherein the optimum columnwidth is obtained when the first color is observed with the first eyeperspective viewer while the second color is observed with the secondeye perspective viewer in step b; e. substituting another of the testimages if the optimum column width magnification was not obtained instep c and repeating steps b, c and d; f. producing a stereoscopic imagefor use in a lenticular stereogram, wherein the stereoscopic imageincludes interdigitated columns each having the optimum column width.16. A method of optimizing the viewing zone of a lenticular stereogramhaving a lenticular screen in intimate juxtaposition with a stereo imagepair, wherein the lenticular screen includes a plurality of individuallenticules and the stereo image pair includes a plurality of columns ofpreset column width each corresponding to an individual lenticule, eachof said columns having alternating image stripes of left eye perspectiveimages and right eye perspective images, comprising adjusting the columnwidth to obtain optical alignment of each column with its correspondinglenticule for a specified viewing position, wherein the adjusting stepcomprises: a. providing a series of test images, wherein each test imageincludes a plurality of columns each corresponding to an individuallenticule of the lenticular screen, and wherein each column has a presetcolumn width, the preset column width being different for each of thetest images, and wherein each column includes at least a first stripe ofa first color and a second stripe of a second color alternating witheach other, and wherein the first color and the second color arevisually distinct; b. holding a first of the test images in intimatejuxtaposition with the lenticular screen; c. observing the test imageand lenticular screen from a specified viewing position with a viewingdevice, wherein the viewing device includes a first eye perspectiveviewer and a second eye perspective viewer; d. determining an optimumcolumn width for the stereo image pair to be viewed from the specifiedviewing position, wherein the optimum column width is obtained when thefirst color is observed with the first eye perspective viewer while thesecond color is observed with the second eye perspective viewer in stepc; e. providing another of the test images if the optimum column widthis not obtained in step d and then repeating steps c and d; and f.producing the stereo image pair to have interdigitated columns eachhaving the optimum column width.